Charge controller

mdm1mdm1 Registered Users Posts: 7
I am looking to replace my charge controller with one alittle more reliable. Here is my system. I have a remote cabin with unobstructed south exposure for my panels. System-2 12v 130 watt panels(260w), 1800w charger inverter, 4 6v 220 amp hour batteries wired for 12v. I know this is a small system but it serves my needs. What would the recommended charge controller be? I would like a mppt. The one I have now is not very reliable and I have had it replaced more than once. The brand is not important. Thanks for any and all help. Mike


  • garlicgarlic Solar Expert Posts: 43
    Re: Charge controller

    The Rogue MPPT would be perfect for your situation:

    It would also allow you to increase the size of your array so that you

    could meet the C/20 minimum charge rate(~22 amps in your case) that your batteries are craving.

    Around the 400w mark with MPPT would get you into that range.

    The Morningstar MPPT 45 would get you to the C/10 rate which is optimum and about $200 more all said and done.
  • BB.BB. Super Moderators, Administrators Posts: 33,327 admin
    Re: Charge controller

    Not a problem--Small is beautiful (really, for most of us, small is cheap ;)).

    Just a quick look at the system--Batteries should be charged at ~5-13% rate of charge, and assuming a 0.77 derating solar panels+charge controller:
    • 2 parallel strings * 220 AH = 440 AH @ 12 volt bank
    • 440 AH * 14.5 volts charging * 1/0.77 derating * 0.05 rate of charge = 414 watts minimum recommended solar array
    • 440 AH * 14.5 volts charging * 1/0.77 derating * 0.13 rate of charge = 1,077 watts cost effective maximum recommended solar array
    So--If you went for a larger solar array, an MPPT controller would probably be worth the MPPT charge controller.

    For a 260 watt array, it is a bit on the small side to get much improvement from a MPPT controller, UNLESS, you have a long wiring run from the array to the battery shed/charge controller.

    If you are not planning on going for a bigger system and want to look at MPPT:

    Morningstar SunSaver 15 Amp MPPT Solar Charge Controller Price: $217.00 (get the remote temp sensor option--about required for this guy)

    If you were looking to go larger (~2x for 12 volt bank), the Rogue 30 amp 12/24 volt MPPT is a very good bang for the buck. New model has a remote battery voltage sense connection.

    And MorningStar has two more MPPT controllers, a 45 and 60 Amp which are both very nice:

    Morningstar TriStar 45 amp MPPT solar charge controller Price: $419.00
    Morningstar TriStar 60 amp MPPT solar charge controller Price: $500.00

    MorningStar also makes a wide range of PWM controllers too... Their TS PWM series is very nice--has both remote temperature sensor option (recommended option) and a remote battery voltage sense connection (I like this very much).

    In general, many solar controller manufacturers make a lot of money on options (temp sensors, remote displays, etc.)... So look at the entire package and shipping costs before making up your mind.

    Some other things to think about--MorningStar makes a very nice 300 watt true sine wave 12 volt input inverter that has very efficient and low standby power ratings--Really helpful for smaller systems.

    Otherwise, keep an eye on your battery bank (hydrometer, battery monitor, etc)... Don't over discharge, don't let it set below 75% state of charge for days/weeks/months at a time, and keep up the electrolyte level with distilled water. And avoid taking the battery "dead" with the inverter (below ~20% state of charge).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • lazzalazza Solar Expert Posts: 336 ✭✭✭
    Re: Charge controller

    HI Forum

    this is interesting. I wasnt sure if there was a "minimum charging rate" of 5%.

    For example I was recently looking at an off-grid installation but only for weeekend usage. The client, however, wants to keep a fridge going all week- therefore I had to size up the batteries. But kept the PVs minimal to provide just about enough to store for the weekend in the worst winter month with approx 3 days autonomy. The batteries came out at 1200 Ah and the PV array size at just over 1kWp (24V system).

    The problem this leaves is that, according to what has been mentioned in this thread, that the PV array should be nearer 2kWp- or alternatively the batteries sized at nearer 500 Ah!

    Big differences, can anyone assist?

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Charge controller

    1200 Amp hours? :confused:
    Your first post says four 220 Amp hour 6 Volt batteries. That would be 440 Amp hours @ 12 Volt.

    That much battery could supply up to 2400 Watt hours a day. That's enough to run a refrigerator unless its a real energy hog. I run the whole cabin on that much power.

    The panel size (and here with intermittent power demands you may well be able to use the 5% minimum) would be for 22 Amps peak @ 12 Volts, or about 342 Watts including the typical derating factor. 1kW of array is far more than that and should have no trouble supply a full 10% charge plus.

    Am I missing something? :confused:
  • TheBackRoadsTheBackRoads Solar Expert Posts: 274 ✭✭
    Re: Charge controller

    lazza is not the OP coot...
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Charge controller
    lazza is not the OP coot...

    More brain cells giving up. :blush:

    Situation similar, though.
  • lazzalazza Solar Expert Posts: 336 ✭✭✭
    Re: Charge controller

    sorry to confuse things, maybe a should've started another thread...:blush:
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Charge controller
    lazza wrote: »
    sorry to confuse things, maybe a should've started another thread...:blush:

    No need for you to apologize for my senility. :cool:
  • FullpowerFullpower Solar Expert Posts: 69 ✭✭
    Charge controller

    My favorite PV charge control is the OUTBACK FM-80
    all parameters are adjustable, can work from 12 volt through 60 volt nominal systems, absorb, float voltage and time periods are widely adjustable, and will work with a battery temperature sensor to compensate charge profile with temperature.
    That and unparalleled customer service.
    I like the FM-80 so much, I bought TWO.
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